Dual tank humidifier



FIG. 1 is a top perspective view of a dual tank humidifier showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 as a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines are included for the purpose of illustrating portions of the humidifier that forms no part of the claimed design. 

CLAIM The ornamental design for a dual tank humidifier, as shown and described. 